U.S. Pat. No. 6,038,023 discloses a system for fluorescence detection or fluorescence spectroscopy. The light coming from a sample is in this case split spectrally by means of a prism and is directed onto a detector array.
U.S. Pat. No. 4,674,880 likewise describes a spectrophotometer in which the light to be analyzed impinges on a detector having a multiplicity of detector elements.
German patent specification DE 41 11 903 discloses an invention for spectroscopy-correlated light scanning microscopy. The spectrograph contains a cooled two-dimensional CCD array, on the basis of which the measurement light is detected.
There are three essential architectures of CCD chips, namely full frame, frame transfer and interline transfer chips.
The spectrally split detection light in a laser scanning microscope is intended to be detected by means of a CCD or preferably EMCCD line detector. However, such CCD or EMCCD detectors according to the prior art are too slow with regard to the image recording rate required for many applications.
In the case of full frame chips, the complete area is used for image generation. If a finished exposed image is read out, the pixels that have not yet been read out continue to be subjected to the exposure. Without a mechanical shutter, therefore, smear effects arise.
In the case of a frame transfer chip, half of the chip area is shielded by a light-opaque mask. After exposure, the image information is completely shifted into this light-insensitive part of the chip. Since significantly less time is required for this shifting operation than for subsequently reading the chip, the smear effects are considerably reduced as a result.
A further reduction of the smear effect is realized in the case of interline transfer chips. In the latter, every second column of the chip is masked in light-opaque fashion. After exposure, the image only has to be shifted by one column width.
In the case of full frame chips, the minimum time between two successive exposure operations, the so-called image separation, is generally equal to the read-out time of the image information from the chip. Both in the case of frame transfer chips and in the case of interline transfer chips, the time between two successive exposures can be shorter at most once than the time required for reading out the image information. In a time series having more than two images, in these chips, too, the minimum separation between two successive exposures is equal to the read-out time of the respective data from the masked regions.
The design of frame transfer and interline transfer chips is optimized toward avoiding smear effects that can arise during the operation of reading out the image information items. The minimum separation between successive exposures, i.e. the image separation and thus also ultimately the image repetition rate, is not influenced by the design of said chips.